Скачать или смотреть How to Create a Blob in Terraform Only if it Doesn't Already Exist

Learn how to configure `Terraform` to create a block blob in Azure only if it doesn't exist, ensuring that existing manual changes are preserved.
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This video is based on the question https://stackoverflow.com/q/75210727/ asked by the user 'Pan Wolodyjowsky' ( https://stackoverflow.com/u/4293446/ ) and on the answer https://stackoverflow.com/a/75312127/ provided by the user 'Pan Wolodyjowsky' ( https://stackoverflow.com/u/4293446/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Managing Azure Storage with Terraform: Creating Blobs Without Overwriting

When working with Azure and Terraform, you may encounter scenarios where you need to create resources conditionally. One common requirement is ensuring that a block blob is created only if it doesn't already exist. This situation often arises when blobs may have been modified manually, and you want to avoid overwriting those changes each time you re-run your Terraform code. Let’s explore how to satisfy this requirement effectively.

The Problem: Overwriting Existing Blobs

In your Terraform configurations, you may have something similar to the code snippet below for creating a storage account, container, and blob:

[[See Video to Reveal this Text or Code Snippet]]

When you run your Terraform plan, you might notice that it forces a blob replacement due to changes in content_md5, which is intended to represent the content's hash. If you had previously modified the blob manually, this could lead to data loss.

The Solution: Implementing a Lifecycle Rule

To prevent Terraform from replacing the blob, we can use a lifecycle block within the blob resource definition. This lifecycle block instructs Terraform to ignore changes made to specific attributes, allowing existing content to remain intact.

Step-by-Step Implementation

Here's how you can modify your blob resource definition:

Open Your Terraform Configuration File: Access the file where your storage blob is defined.

Add a Lifecycle Block: Incorporate the lifecycle block to your blob resource, specifically targeting the content_md5 attribute.

Here is your updated blob resource definition:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of Changes

lifecycle Block: The lifecycle block with ignore_changes tells Terraform to skip updates for the content_md5 attribute. This is crucial when the blob may have been changed outside of Terraform.

Benefits of This Approach:

Preserves Manual Changes: By ignoring the content_md5, you prevent Terraform from trying to replace the blob if it's been modified manually.

Simplifies Deployments: Future runs of Terraform can continue without disrupting your existing data.

Conclusion: Putting It All Together

Managing Azure storage with Terraform can be straightforward if you know how to configure your resources correctly. By leveraging the lifecycle features within Terraform, you can create conditions that allow for flexibility and control over your resources.

If you need to ensure that a blob is created only if it doesn't already exist, applying a lifecycle block to ignore changes effectively addresses the problem. This solution maintains the integrity of your data, while still allowing for Terraform's powerful resource management capabilities.

Now you're better equipped to handle blob creation in Terraform without the risk of unintentional overwrites.